The invention relates to continuity and polarity testing apparatus, and more particularily to a tester principally for automotive use, employing a multi-colored light emitting diode capable of emitting different colors for different polarities.
Polarity and continuity testing devices, often in the form of a pencil shaped body with a point or probe at one end and a wire connectable to ground at the other end, have been well known. For example, see U.S. Pat. Nos. 3,964,039, 4,366,434, and 4,527,118.
U.S. Pat. No. 4,366,434 discloses a continuity checker and voltage detector utilizing two or three light emitting diodes for determining the polarity of the voltage with two of the diodes and for checking continuity with the third diode. The tester includes a DC bias source for the first and second light emitting diodes, and a DC supply for the third light emitting diode. In a principal embodiment, the patent includes two parallel circuits, one having a resistance, a battery, a light emitting diode and a rectifier diode, and the other having two separate batteries, two light emitting diodes and a resistance.
Although electrical testers such as disclosed in the above referenced U.S. Pat. No. 4,366,434 have been effective for limited purposes, they have included an unnecessarily high number of components and complexity of circuitry as compared to the present invention, and they have also been of limited capability in comparison to the present invention as described below.